1. Field of the Invention:
This invention relates to a heat exchanger for a radiator or the like, and more particularly to a tank for a heat exchanger in which a seal member is fixedly secured to a skirt portion of the tank, and a method of producing such a tank. The present invention further relates to an injection mold used for forming a resin seal member of the tank.
2. Description of the Related Art:
A conventional heat exchanger tank is shown in FIG. 1, in which a resin is injected into an annular groove 15 of a dovetail-shaped cross-section, formed in a skirt portion 13 of the tank 11, to mold a seal member 17 which is fixedly secured to the annular groove 15. Hence, disengagement of the seal member 17 from the tank 17 is highly unlikely.
In such a heat exchanger tank, the annular groove 15 of a dovetail cross-section must be formed on the skirt portion 13 of the tank 11. However, this shape of the annular groove 15 makes it very difficult to remove the tank 11 from a resin from which the tank 11 is molded.
One known heat exchanger tank-producing method which has solved such a problem is disclosed in Japanese Patent Unexamined Publication No. 3-138116.
Such a heat exchanger tank-producing method produces a tank as shown in FIG. 2, in which an annular groove 15 having a rectangular cross-section is formed in an open end surface of an annular skirt portion 13, which is formed over the entire periphery of an open end of a resin tank 11. The skirt portion 13 is received in a space formed by molds 18, 19 and 21.
An outer side surface 13a and an inner side surface 13b of the skirt portion 13 are held by molds 21 and 19, respectively, and the outer side surface 13a and the inner side surface 13b are urged toward each other by a projection 21a formed on the surface of each mold 21 facing the outer surface 13a of the skirt portion 13. Seal resin 23 is injected into the annular groove 15 and a seal-forming space 19a which is formed in the mold 19 opposed to the annular groove 15. The seal resin 23 solidifies, thereby producing the heat exchanger tank as shown in FIG. 1.
However, in such a conventional heat exchanger tank-producing method, the skirt portion 13 is deformed merely by pressing the projection 21a against the outer surface 13a. Therefore, it is difficult to deform the skirt portion 13 into a predetermined shape. Furthermore, cracks are likely to develop at the portion of the skirt portion 13 disposed laterally to the bottom surface 15a of the annular groove 15.
That is, the heat exchanger tank 11 is formed of a reinforced resin having glass fibers added to a nylon resin, and the tank has an elongated shape having one open end. Therefore, during molding, the tank is susceptible to twisting as well as deformation due to the expansion of its open end.
For example, the skirt portion 13 of the tank 11 having the outwardly-expanded open end is set on the mold 18 as shown in FIG. 3. Then the molds 19 and 21 are then moved toward the skirt portion 13, so that the upper end of the inner surface 13b of the skirt portion 13 of the tank 11 is positioned by the mold 19. In this condition, when the outer surface 13a of the skirt portion 13 of the tank 11 is pressed by the projections 21a of the molds 21, the outer surface 13a is deformed to a large extent by this pressing.
Since that portion of the skirt portion 13, defining one side wall of the annular groove 15 having the outer surface 13a, has a small thickness, deformation develops at that portion of the skirt portion 13 disposed laterally of the bottom surface 15a of the annular groove 15. Hence, it is likely that a crack may develop at this portion.
In a conventional heat exchanger tank that is produced by conventional methods, bubbles are formed in the resin injection-molded seal member 17 at a position located opposite to an injection gate.
In particular, a seal resin 23, injected from the injection gate 25, is divided in opposite directions at this injection gate 25, and flows toward the gate-opposite position 27 through an annular groove 15 in the tank 11 and a seal-forming space in a mold 19, as indicated by arrows in FIG. 4. However, since the temperature of the mold 19 is higher than the temperature of the tank 11, the fluidity of the seal resin 23 in the seal-forming space 19a becomes higher than the fluidity of the seal resin in the annular groove 15.
As a result, in the vicinity of the gate-opposite position 27, the seal resin 23 in the seal-forming space 19a is closer to the gate-opposite position 27 than is the seal resin 23 in the annular groove 15, as shown in FIG. 5A. Hence, immediately before the opposite ends of the seal resin 23 impinge on each other at the gate-opposite position 27, an air reservoir portion 28 is formed at the bottom surface of the annular groove 15 as shown in FIG. 5B. Then, when the opposite ends of the seal resin 23 are joined together at the gate-opposite position 27, bubbles 29 are formed in the seal resin 23, and also a space 30 in which the seal resin 23 is absent is formed, as shown in FIG. 5C.
In addition, in the conventional injection mold used for producing a tank, since a runner is formed in a sprue of a mold, it is very difficult to separate the runner from the mold 19.